replacing "myfile.xlsx" with your filename, which can be absolute or relative. This connects to a file
on your local machine. You then create your PMF/EMF as normal and use JDO/JPA as normal.

There are tutorials available for use of DataNucleus with Excel
for JDO and
for JPA

Things to bear in mind with OOXML usage :-

Querying can be performed using JDOQL or JPQL. Any filtering/ordering will be performed
in-memory

Relations : A spreadsheet cannot store related objects directly, since each object is a
row of a particular worksheet. DataNucleus gets around this by storing the String-form of
the identity of the related object in the relation cell.